1. Field of the Invention
The present invention relates generally to apparatus for screening, separating or grading materials, principally for use in the mining industry. The present invention is particularly directed to arrangements for fixing screen panels to the support frame of a vibratory screening machine and to the screen panels themselves. The system and panels are applicable for screening, separating and grading ores and other materials, and it will be convenient to hereinafter describe the invention in relation to that use. It is to be appreciated, however, that the invention is not limited to such apparatus and use.
2. Description of the Prior Art
The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.
Screening apparatus of the type with which the invention is concerned is generally used for screening, grading, or separating materials such as ores and comprises an array of screen panels which are removably fixed to a frame to provide a continuous screen deck. The material to be screened is fed onto the deck at one end and the apparatus is vibrated so that the material moves over and through its screening surface.
One form of screen panel includes a steel frame moulded within a resilient plastic material, such as polyurethane. See for example Australian Patent No. 577767 (66006/86) (also published as U.S. Pat. No. 4,674,251). The plastic moulding forms the major part of the panel and it is in the plastic moulding that the openings for screening are provided.
The screen panels in a screen deck are usually subject to wear, due to the abrasiveness of the mining materials typically being screened, and thus the screens require periodical replacement. This presents a difficulty with the attachment of the panels to the deck frame, as the attachment must be secure and robust, but should also be releasable in a manner that is quick and easy.
The frame to which screen panels in a screen deck are secured usually comprises a framework of elongate beams. The beams can be of various section, but the present invention has been developed for the connection of the support panels to a top or upstanding edge of a beam.